The Phase I study demonstrated that a compound tracheal prosthesis consisting of a rigid outer layer and an inner biodegradable layer can successfully replace 7.5 cm of cervical trachea in the dog without infection, rejection, or extrusion. The prothesis permitted intraluminal epithelization by growth and migration and by free operative buccal mucosal grafts. The Phase II study will continue to evaluate a rigid compound tracheal prosthesis as a replacement for 4-6 cm of cervical trachea. A second study will evaluate a rigid compound tracheal patch to widen the tracheal and sub-glottic lumen in lambs raised to maturity. A third study will develop and evaluate a flexible compound tracheal prosthesis to replace up to 10 cm of thoracic trachea. Methods to increase the rate of epithelization of the prosthetic lumen using incorporation of growth factors, extracellular basement membrane matrix on the inner layer, free operative buccal mucosal grafts, and in-vitro preoperative tissue culture grafting will be evaluated.